Grate



Oct. 31, 1944. 4 SCHRAGVE 2 ,361,796

' GRATE Filed June 17, 1940 2 Sheets-Sheet l F. R. SCHRAGE Oct. 31-, 1944;

GRATE Filed June 17, 1940 2 Sheets-Sheet 2 IYVEIV. UT

Patented Oct. 31, 1944 t UNITED STATES PATENT OFFICE GRATE Franklin R. Schrage, Riverside, .l1l., assignor to Interlake Iron Corporation, Chicago, 111., a corporation of New Yo rk Application June 17, 1940, Serial No. 340,972

1 Claim. (01. 126-163) This invention relates to grates for furnaces, and more particularly to auxiliary grates designed to be placed on top of the ordinary fiat grates of domestic furnaces in order to make the furnaces operate better, particularly with certain fuels, such as coke. In particular, this invention relates to auxiliary grates of the type which, although not indispensable, are desirable foruse in the Coke burning system described in my copending application filed April 17, 1940, Serial No. 330,152, now Patent Number 2,344,328, March 14, 1944.

One of the principal objects of thepresent invention is to provide an auxiliary grate of the type described above and having air passages designed to preheat the air passing through the auxiliary grate to the coke being burned.

Another object of this invention is to provide an auxiliary grate whose outer or upper surface is constructed to support the fire bed and to prevent the ash or coke forming parts of the fire bed from sliding down the sides of the grate.

Another object of the present invention is to provide an auxiliary grate having the discharge openings of the air passages located in such a way as to minimize the falling of ashes or coke through them.

v The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claim. My invention itself, both as to its organization and manner of construction, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

Figure 1 is a cross section through an ordinary domestic furnace or boiler, showing one of the preferred forms of the invention in place;

Figure 2 is a plan view of the form of the in vention shown in Figures 1; and

Figure 3 is a cross section on the line III-II[ of Figure 2 with a portion of the auxiliary grate shown in elevation and with the adjacent portions of the main grate and the fire bed also shown.

The auxiliary grate Ill, which is shown in the drawings and which forms one Of the preferred embodiments of the invention, may be employed, for example, in a conventional domestic boiler ll having water spaces 12 surrounding the fire pot l3 and provided with grates M at the bottom of the fire pot. The grates I4 are of the common horizontal type formed of a plurality of bars adapted to support the fire bed.

. The boiler II is provided with a base portion i5 containingthe ash pit l6 below the grates, and means such as a blower ll, are preferably provided for raising the pressure of the air in the ash pit l6 slightly above atmospheric and thus providing a forced draft. The blower i1 is pro-. vided with conventional controls, as more fully described in my above mentioned copending application, for regulating the supply of air in accordance with the amount of heat desired. The boiler H may also be provided with an automatic stoker of the type adapted to feed fuel'to the top of the fire, as disclosed in my above mentioned copending application, or the fuel may be fed by hand.

' The auxiliary grate H] is a thick conical cast iron shell formed with a plurality of feet l8 projecting down from its base or rim and having a plurality of air passages I9 extending up through it. The feet [8 fit down between the horizontal grate bars M and positively prevent lateral shifting of the auxiliary grate [0 on the main grate l4. They may also look the main grate l4 so that it cannot be shaken. i

The interior or lower surface of the auxiliary grate i0 is a smooth cone interrupted only by the openings or entrances of the air passages l9. The outer or upper surface of the grate I0 is formed in a plurality of similar sections, each of which comprises a steep conical surface 20, an annular horizontal step or shelf 2|, a short steep conical surface 22, another short but very steep conical surface 23, and a second annular horizontal step "24, arranged successively one above the other as shown in Figure 3. This arrangement of successive conical and horizontal surfaces is repeated several times from the bottom of the grate to the top, so that there are several similar short steep conical surfaces 22 spaced up the side of the grate, the upper ones being smaller in diameter than the lower ones but all having substantially the same height and slope. The upper or outlet ends of the air passages l9 are located in the short steep conical sections 22 and occupy their entire width, So that these sections of the surface consist only of bridges joining the shelves 2| and the very steep conical sections'23. This particular feature is not essential, but it is desirable that the outlets of the air passages 19 be located in steep conical surfaces, such as the surfaces 22, and that there be at least one horizontal shelf 2| or 24 close to the openings.

When the grate I0 is in use, its lower portion is located in a bed of ashes 21 which supports a generally fiat annular clinker 28. The clinker 28 and the upper portion of the grate I0 support of the coke 29 which is above the clinker 28, and.

enabling that portion of the coke 29 to burn.

Air also flows up between the grate bars I24 around the auxiliary grate [0, through the bed of ashes 21 and the porous clinker" 2-8 to support the combustion of that portion of the coke; which lies near the side l3 of the furnace. As

the combustion of the coke 29' proceeds-over a.

period of several days, the clinker 28 grows in thickness and encroaches in more and more on the: auxiliary grate Hi. Itthen becomesnecessary tobreak up the clinkenand remove it, disturbing the remainder of th fire. bed. as little as: possible while this is being done, as" is explained more fully in my copending application referredrto above.

It'will be notedfrom the-portion of the auxiliaiiy grate l[l-shoWn.in'v section; iniFigure 3% that the air passages [9- are much larger at. their lower or inlet endsthan attheir upper or outlet ends,, and that their cross-sectional area thus decreases in: the direction inwhichthe air flows through? them. I-t will also benoted-that theiron casting which forms the auxiliary grate I0. is of substantial thickness, especially near the top. Because of this, the air flowing upwardly through the passages I9 is within the passages for a suificient length of time to-receive a substantial amount of heat-from the sides of the-passages, especially in. the passages in the upper and thicker portion of the grate Ill. Theair is therefore preheated before it reaches the fire. and it also serves to keep the grate, which. is indirect contact with thefire, from being heated to too higha temperature.- Thegreater thickness: of the metal in: the upper partof the'grate' It) not only: makes theair passages l-Q therein: longer so: that. more. heat will beabsorbed. by the air flowing through the air passages. but also provides more metal for conducting theheat to the lower. and cooler portions of the grate: II];

It will be noted from Figure 3,.thatthe' annular horizontal steps 2| and 24-serveto carry a great part of the Weight of the ashes andthepressure upon them caused by the Weight of'theclinker 28 andthe coke 29. The ashes.2-'|=a1so:bear down upon the conical. surfaces 20,22 and 23, but very littleof the weight of the. ashes comesauponl the conical surface: 22 in whichthe airpassages: I 9

open. Because of this, very little ash will fall into the air passages 19 thus making it easier to maintain a bed of ashes 21 of the desired thickness in the furnace. It will also be noted that all of the sides of the air passages H! are either vertical or diverge down away from the vertical, so that any ash which may fall into one of the air passages 19 will fall clear through it" and not cause any obstruction therein. Thus the air passages I9 will always be clear for air to flow freely through them.

The particular shape which I have given to the air passages 19 not only provides for improved preheating of the air and prevents their being clogged or partially clogged with ashes, but it alsomakes the manufacture of the grate more economical than would otherwise be possible.

Because all of the sides of the air passages l9 are either vertical or diverge downwardly, it is practicalto prepare a mold for casting the grate by using asimpleonepiece patternand: without usingv any previously preparedcores whatsoever. 'I hemold. is. prepared: with. the sand'in the drag or bottom part of the. molding flask extending r up. in. the passages ill to their upper ends, and

these portions of themold. arewell tamped and suitably reenforced with. iron wires, if necessary, so that they will. have the required strength.

From the above it will be seen that I have designed an auxiliary grate to which isespecially Well suited for the purpose for which it is designed, and which is also relatively inexpensive to construct. My invention ,,therefore,' is not only efiicient in operation but is simple and cheapto produce.

It. willof" course be. understood that the particular form of. my invention which has been described abovev and is.- shown in the accompanying; drawings, is disclosed onlyby Way of illustration and that the invention is not limited to this particular form The invention includes not only this particular form. but any form falling within. the scope. of. the followingv claim.

Lclaim as-my invention;

A generallyconicallyshaped grate having an exterior surface provided witha series. of. annular ledges lying in vertically spaced. horizontal planes and connected by conical wall portions which extend. from. the inner annular edge of one ledge to: the outer annular edge of the. next succeeding ledge thereabove, said grate having atplunality of ducts therethrough each of which emerges on. the. exterior side of the grat at the junctions of-i theconical Wall. portions. and the inner edges of the ledges; said. ducts having" two segmental cylindrical Wall portions which diverge obliquely downwardly from their respective exterior openings.

FRANKLIN- Rh. SCHRAGE. 

